Compaq AlphaServer DS20 Service Manual

AlphaServer DS20Service ManualOrder Number: EK–AS140–SV. A01This manual is for anyone who services this system. It includestroubleshooting informatio

xDocumentation TitlesTable 1 lists books in the documentation set.Table 1 AlphaServer DS20 DocumentationTitle Order NumberUser and Installation Docu

4-10 AlphaServer DS20 Service Manual4.5 Memory Module Removal and ReplacementCAUTION: Several different memory DIMMs work in these systems. Be sur

Removal and Replacement 4-11Removal1. Shut down the operating system and turn the system off.2. Expose the card cage side of the system (see Section

4-12 AlphaServer DS20 Service Manual4.6 System Board Removal and ReplacementFigure 4-5 Removing System BoardModuleBraceSystem BoardPK1498-98

Removal and Replacement 4-13Removal1. Shut down the operating system and turn the system off.2. Unplug the AC power cord. (Auxiliary power is appli

4-14 AlphaServer DS20 Service Manual4.7 PCI/ISA Option Removal and ReplacementFigure 4-6 Removing PCI/ISA OptionSlot CoverScrewsOption CardIP00225

Removal and Replacement 4-15Removal1. Shut down the operating system and turn the system off.2. Expose the card cage side of the system (see Section

4-16 AlphaServer DS20 Service Manual4.8 Server Feature Module Removal andReplacementFigure 4-7 Removing Server Feature ModuleFAN0FAN1PK1403-98Serv

Removal and Replacement 4-17Removal1. Shut down the operating system and turn the system off.2. Unplug the AC power cords. (Auxiliary power is appl

4-18 AlphaServer DS20 Service Manual4.9 Power Supply Removal and ReplacementFigure 4-8 Removing Power Supply4 rear screws6/32 inchInternal screw 3

Removal and Replacement 4-19Removal1. Shut down the operating system and turn the system off.2. Expose the power section of the system (see Section

System Overview 1-1Chapter 1System OverviewThe Compaq AlphaServer DS20 system consists of up to two CPUs, up to 4 Gbytes ofmemory, 6 I/O slots, and

4-20 AlphaServer DS20 Service Manual4.10 Power Harness Removal and ReplacementFigure 4-9 Removing Power HarnessPK1404-99

Removal and Replacement 4-21Removal1. Shut down the operating system and power down the system.2. Remove the AC power cords. (Auxiliary power is ap

4-22 AlphaServer DS20 Service Manual4.11 Power Transition Module Removal andReplacementFigure 4-10 Removing Power Transition ModulePK1402-98

Removal and Replacement 4-23Removal1. Shut down the operating system and turn the system off.2. Remove the AC power cords.3. Expose both the card ca

4-24 AlphaServer DS20 Service Manual4.12 Auxiliary Fan Removal and ReplacementFigure 4-11 Removing Auxiliary FanPK1481 - 98Power TransitionModule

Removal and Replacement 4-25Removal1. Shut down the operating system and power down the system.2. Unplug the AC power cord.3. Expose the power secti

4-26 AlphaServer DS20 Service Manual4.13 System Fan Removal and ReplacementFigure 4-12 Removing System FanFAN0FAN1Module GuidesPK1400-98

Removal and Replacement 4-27Removal1. Shut down the operating system and turn the system off.2. Unplug the AC power cord. (Auxiliary power is appli

4-28 AlphaServer DS20 Service Manual4.14 Cover Interlock Removal and ReplacementFigure 4-13 Removing Cover InterlockPKW0519A-97InterlockSwitch12

Removal and Replacement 4-29Removal1. Shut down the operating system and turn the system off.2. Expose the card cage side of the system (see Section

1-2 AlphaServer DS20 Service Manual1.1 System EnclosureThe system has up to two CPU modules and up to 4 Gbytes of memory. A singlefast wide Ultr

4-30 AlphaServer DS20 Service Manual4.15 Operator Control Panel Removal and ReplacementFigure 4-14 Removing OCPPKW-0501A-97OCP

Removal and Replacement 4-31Removal1. Shut down the operating system and turn the system off.2. Expose the card cage side of the system (see Section

4-32 AlphaServer DS20 Service Manual4.16 CD-ROM Removal and ReplacementFigure 4-15 Removing CD-ROMPKW0519-97

Removal and Replacement 4-33Removal1. Shut down the operating system and turn the system off.2. Expose the card cage side of the system (see Section

4-34 AlphaServer DS20 Service Manual4.17 Floppy Removal and ReplacementFigure 4-16 Removing Floppy1PK1401-98

Removal and Replacement 4-35Removal1. Shut down the operating system and turn the system off.2. Unplug the AC power cords.3. Expose the card cage si

4-36 AlphaServer DS20 Service Manual4.18 SCSI Disk Removal and ReplacementFigure 4-17 Removing StorageWorks DiskPKW0501B-97

Removal and Replacement 4-37Removal1. Shut down the operating system and turn the system off.2. Open the front door exposing the StorageWorks disks.

4-38 AlphaServer DS20 Service Manual4.19 StorageWorks Backplane Removal andReplacementFigure 4-18 Removing StorageWorks BackplaneStorageWorksBackp

Removal and Replacement 4-39Removal1. Shut down the operating system and turn the system off.2. Unplug the AC power cords.3. Expose the power sectio

System Overview 1-3The numbered callouts in Figure 1-1 refer to the system components.➊System card cage, which holds the system board and the CPU, m

4-40 AlphaServer DS20 Service Manual4.20 StorageWorks UltraSCSI Bus Extender Removaland ReplacementFigure 4-19 Removing StorageWorks UltraSCSI Bus

Removal and Replacement 4-41Removal1. Shut down the operating system and turn the system off.2. Unplug the AC power cords.3. Expose the power sectio

Halts, Console Commands, and Environment Variables A-1Appendix AHalts, Console Commands, andEnvironment VariablesThis appendix discusses halting the

A-2 AlphaServer DS20 Service ManualA.1 Halt Button FunctionsThe Halt button causes the system to perform in various ways depending uponthe system st

Halts, Console Commands, and Environment Variables A-3A.2 Using the Halt ButtonUse the Halt button to halt the Compaq Tru64 UNIX or OpenVMS operatin

A-4 AlphaServer DS20 Service ManualA.3 Halt AssertionA halt assertion allows you to disable automatic boots of the operating system sothat you ca

Halts, Console Commands, and Environment Variables A-5by the RCM reset command to force a halt assertion. Upon reset, the system powersup to the SR

A-6 AlphaServer DS20 Service ManualA.4 Summary of SRM Console CommandsThe SRM console commands are used to examine or modify the system state.Tab

Halts, Console Commands, and Environment Variables A-7Table A-2 Summary of SRM Console Commands (Continued)Command Functionlogin Turns off secure

1-4 AlphaServer DS20 Service Manual1.2 Operator Control Panel and DrivesThe control panel includes the On/Off, Halt, and Reset buttons and an LCDd

A-8 AlphaServer DS20 Service ManualA.5 Summary of SRM Environment VariablesEnvironment variables pass configuration information between the console

Halts, Console Commands, and Environment Variables A-9Table A-3 Environment Variable Summary (Continued)EnvironmentVariable Functionmemory_test Sp

A-10 AlphaServer DS20 Service ManualA.6 Recording Environment VariablesThis worksheet lists all environment variables. Copy it and record the setti

Halts, Console Commands, and Environment Variables A-11Table A-4 Environment Variables Worksheet (Continued)EnvironmentVariable System Name System

Managing the System Remotely B-1Appendix BManaging the System RemotelyThis appendix describes how to manage the system from a remote location using

B-2 AlphaServer DS20 Service ManualB.1 RCM OverviewThe remote console manager (RCM) monitors and controls the system remotely.The control logic resi

Managing the System Remotely B-3B.2 First-Time SetupTo set up the RCM to monitor a system remotely, connect the modem to theCOM1 port at the back of

B-4 AlphaServer DS20 Service ManualB.2.1 Using RCM Locally or with a Modem on COM1Use the default escape sequence to invoke the RCM mode locally fo

Managing the System Remotely B-5B.3 RCM CommandsThe RCM commands given in Table B-1 are used to control and monitor asystem remotely.Table B-1 RCM

System Overview 1-5➊ On/Off button. Powers the system on or off. When the LED to the right of thebutton is lit, the power is on. The On/Off butto

B-6 AlphaServer DS20 Service ManualCommand Conventions• The commands are not case sensitive.• A command must be entered in full.• You can delete an

Managing the System Remotely B-7help or ?The help or ? command displays the RCM firmware commands.poweroffThe poweroff command requests the RCM to p

B-8 AlphaServer DS20 Service ManualquitThe quit command exits the user from command mode and reconnects the serialterminal to the system console por

Managing the System Remotely B-9statusThe status command displays the current state of the system sensors, as well as thecurrent escape sequence and

B-10 AlphaServer DS20 Service ManualB.4 Using the RCM SwitchpackThe RCM operating mode is controlled by a switchpack on the server featuremodule lo

Managing the System Remotely B-11Uses of the SwitchpackYou can use the RCM switchpack to change the RCM operating mode or disable theRCM altogether.

B-12 AlphaServer DS20 Service ManualResetting the RCM to Factory DefaultsYou can reset the RCM to factory settings, if desired. You would need to d

Managing the System Remotely B-13B.5 Troubleshooting GuideTable B-3 is a list of possible causes and suggested solutions for symptoms youmight see.T

Firmware Update C-1Appendix CFirmware UpdateThis appendix provides instructions on updating firmware.Sections in this chapter are:• Updating Firmwar

1-6 AlphaServer DS20 Service Manual1.3 System ConsolesThere are two console programs: the SRM console and the AlphaBIOS console.SRM Console Prompt

C-2 AlphaServer DS20 Service ManualC.1 Updating Firmware and ConsolesStart the Loadable Firmware Update (LFU) utility by issuing the lfu commandat t

Firmware Update C-3• From the SRM console, start LFU by issuing the lfu command (seeExample C–1). Also from the SRM console, LFU can be booted from

C-4 AlphaServer DS20 Service ManualC.1.1 Updating Firmware from the CD-ROMInsert the Alpha CD-ROM, start LFU, and select cda0 as the load device.Ex

Firmware Update C-5➊ Select the device from which firmware will be loaded. The choices are theinternal CD-ROM, the internal floppy disk, or a networ

C-6 AlphaServer DS20 Service ManualExample C–3 Updating Firmware from the CD-ROM (Continued)UPD> update *

Firmware Update C-7➎ The update command updates the device specified or all devices. In thisexample, the wildcard indicates that all devices support

C-8 AlphaServer DS20 Service ManualC.1.2 Updating Firmware from Floppy Disk — Creating the DiskettesCreate the update diskettes before st

Firmware Update C-9Example C–4 Creating Update Diskettes on an OpenVMSSystemConsole update diskette$ inquire ignore "Insert blank HD floppy i

C-10 AlphaServer DS20 Service ManualC.1.3 Updating Firmware from Floppy Disk — Performing the UpdateInsert an update diskette (see Sectio

Firmware Update C-11➊ Select the device from which firmware will be loaded. The choices are theinternal CD-ROM, the internal floppy disk, or a netwo

System Overview 1-7SRM ConsoleThe SRM console is a command-line interface used to boot the Compaq Tru64 UNIXand OpenVMS operating systems. It also

C-12 AlphaServer DS20 Service ManualExample C–5 Updating Firmware from the Floppy Disk(Continued)UPD> update pfi0

Firmware Update C-13➍ The update command updates the device specified or all devices.➎ For each device, you are asked to confirm that you want to up

C-14 AlphaServer DS20 Service ManualC.1.4 Updating Firmware from a Network DeviceCopy files to the local MOP server’s MOP load area, start LFU, and

Firmware Update C-15Before starting LFU, download the update files from the Internet. You will need thefiles with the extension .SYS. Copy these fi

C-16 AlphaServer DS20 Service ManualExample C–7 Updating Firmware from a Network Device(Continued)UPD> update * -all

Firmware Update C-17➍ The update command updates the device specified or all devices. In thisexample, the wildcard indicates that all devices suppor

C-18 AlphaServer DS20 Service ManualC.1.5 LFU CommandsThe commands summarized in Table C–2 are used to update system firmware.Table C–2 LFU Comma

Firmware Update C-19displayThe display command shows the physical configuration of the system. Display isequivalent to issuing the SRM console comma

C-20 AlphaServer DS20 Service ManuallistThe list command displays the inventory of update firmware on the CD-ROM,network, or floppy. Only the device

Index-1Index?? command, RCM · B-7AArchitecture, block diagram · 1-8Alpha 21264 microprocessor · 1-8, 1-11Alpha chip composition · 1-11AlphaBIOS consol

1-8 AlphaServer DS20 Service Manual1.4 System ArchitectureAn Alpha microprocessor chip is used in this system. The CPU, memory, and theI/O module

Index-2auto_action · 2-7os_type · 2-7Error registers · 3-1exit command, LFU · C-3, C-7, C-13, C-17, C-18, C-19External Interface Address register · 3-

Index-3Memory Management Status Register · 3-3MISC register · 3-9Miscellaneous Register · 3-9MM_STAT register · 3-3Modemusing in RCM · B-3OOperating t

Index-4removal and replacement · 4-16setesc command, RCM · B-8SRM console · 1-7, 2-7status command, RCM · B-9StorageWorks · 1-39backplane removal and

System Overview 1-9The AlphaServer DS20 is a switch-based interconnect system; it uses a cross-barswitch chipset that allows data to move directly f

NoticeThe information in this publication is subject to change without notice.COMPAQ COMPUTER CORPORATION SHALL NOT BE LIABLE FOR TECHNICALOR EDITORIA

1-10 AlphaServer DS20 Service Manual1.5 CPU TypesThere is a single CPU variant.Figure 1-5 CPU Module PlacementCPU 0CPU 1CChipDChipDChipDChipDCh

System Overview 1-11Alpha Chip CompositionThe Alpha 21264 chip uses 0.35 micron chip technology, has a transistor count of 15.2million, consumes 50

1-12 AlphaServer DS20 Service Manual1.6 MemoryMemory consists of up to four memory options, each consisting of four DIMMs.There are four option va

System Overview 1-13Memory VariantsMemory is organized on two 256 plus ECC bit buses. Each bus can hold up to twomemory banks (a memory option) mad

1-14 AlphaServer DS20 Service Manual1.7 Memory Addressing and Data LocationMemory addressing is contiguous beginning with memory bank 0. The firs

System Overview 1-15Memory AddressingThe first address of each bank is one above the ending address of the previous bank.Example 1–1 and Figure 1-8

1-16 AlphaServer DS20 Service Manual1.8 System BoardThe system board contains five major logic sections performing five majorsystem functions.Figu

System Overview 1-17Three major sections on the system board are:• The cross-bar switch chipset and the system components attached to it (CPU(s),mem

1-18 AlphaServer DS20 Service Manual1.8.1 Cross-Bar Switch and System ComponentsThe cross-bar switch chipset consists of a single control chip, t

System Overview 1-19Each type of bus in the system is unique:• The two memory data buses operate in 256-bit mode passing two hex words (32bytes) of

iiiContentsPreface ... ixChapter 1 System Overview1.1 System Enclosure..

1-20 AlphaServer DS20 Service Manual1.8.2 I/O SubsystemThe I/O subsystem consists of two 64-bit PCI buses. One has an embedded ISAbridge, three

System Overview 1-21Table 1-1 PCI Slot NumberingSlot PCI0 PCI1 ISA Shared5 PCI to ISA bridge ISA device logically6 Adaptec SCSI7 PCI slot PCI slot

1-22 AlphaServer DS20 Service Manual1.8.3 System Board SwitchpacksThere are two switchpacks on the system board. They control the writing of the

System Overview 1-23Figure 1-12 shows the location of the switchpacks and Table 1-2 and Table 1-3describe what each switch controls.Table 1-2 Swit

1-24 AlphaServer DS20 Service Manual1.9 Server Feature ModuleThe server feature module provides remote control operation of the system. Afour-swi

System Overview 1-25The system allows both local and remote control. The remote control firmware and aset of switches that enable or disable remote

1-26 AlphaServer DS20 Service Manual1.9.1 Power Control LogicThe power control logic is on the server feature module.Figure 1-14 Power Control

System Overview 1-27The power control logic performs these functions:• Monitors system temperature and powers down the system 30 seconds after itdet

1-28 AlphaServer DS20 Service Manual1.10 Power Circuit and Cover InterlockPower is distributed throughout the system and mechanically can be broke

System Overview 1-29Figure 1-15 shows the distribution of the power enable circuit through the system.Opens in the circuit, or the RCM signal RCM_DC

ivChapter 3 Error Registers3.1 Ibox Status Register - I_STAT...3-23.2 Memory Managemen

1-30 AlphaServer DS20 Service Manual1.11 Power SupplyTwo power supplies provide system power.Figure 1-16 Back of Power Supply and LocationCurren

System Overview 1-31DescriptionA single 675 watt power supply provides power to the system. A second powersupply (optional) provides redundant powe

1-32 AlphaServer DS20 Service Manual1.12 Power Up/Down SequenceSystem power can be controlled manually by the On/Off button on the OCP orremotely

System Overview 1-33When AC is applied to the system, Vaux (auxiliary voltage) is asserted and is sensedon the server feature module. If the On-Off

1-34 AlphaServer DS20 Service Manual1.13 TIG BusThe Timing, Interrupt, and General bus (TIG) performs a number of functions;it carries all system

System Overview 1-35Figure 1-18 is a block diagram of the TIG bus implemented through the TIG chip.Three system functions are carried out on this bu

1-36 AlphaServer DS20 Service Manual1.14 Maintenance Bus (I2C Bus)There are two I2C buses (referred to as the “I squared C bus”) in this system.Th

System Overview 1-37MonitorThe I2C bus monitors the state of system conditions scanned by the power controllogic. There are two registers that the

1-38 AlphaServer DS20 Service Manual1.15 StorageWorks DrivesThe system supports up to seven StorageWorks drives.Figure 1-20 StorageWorks Drive L

System Overview 1-39The StorageWorks drives are to the right of the system cage. Up to seven drives fitinto the shelf. The system supports fast wi

vAppendix B Managing the System RemotelyB.1 RCM Overview...

Troubleshooting 2-1Chapter 2TroubleshootingThis chapter describes troubleshooting during power-up and booting. It also describesthe console test

2-2 AlphaServer DS20 Service Manual2.1 Troubleshooting During Power-UpPower or other problems can occur before the system is up and running.Power

Troubleshooting 2-3If the system does not power up• Are the power cords plugged in?• Is the power supply functioning? (The power supply will shut

2-4 AlphaServer DS20 Service Manual2.2 Control Panel Display and TroubleshootingThe control panel display indicates the likely device when testing

Troubleshooting 2-5Table 2-1 Control Panel DisplayContent of Display Progress Indicated in Power-Up FlowCompaq CPU functioning, path to the OCP

2-6 AlphaServer DS20 Service Manual2.3 Power-Up Display and TroubleshootingIf the power-up display appears, the following hardware is at least par

Troubleshooting 2-7By the time the power-up display is completed,1. the CPUs have run their self-tests,2. the SROM has completed its preliminary t

2-8 AlphaServer DS20 Service Manual2.4 Running Diagnostics — Test CommandThe test command runs diagnostics on the entire system, CPU devices, memo

Troubleshooting 2-92.5 Testing an Entire SystemA test command runs all exercisers for subsystems and devices on the system.I/O devices tested are

viFigures1-1 System Enclosure...1-21-2 Cover Interlock C

2-10 AlphaServer DS20 Service ManualID Program Device Pass Hard/Soft Bytes Wrtn Bytes Rd-------- ------------ ---------- ----- -

Troubleshooting 2-112.6 Other Useful Console CommandsSeveral console commands can be used to diagnose the system.The show power command identifies

2-12 AlphaServer DS20 Service Manual2.7 Troubleshooting with LEDsDuring power-up, reset, initialization, or testing, diagnostics are run on CPUs,m

Troubleshooting 2-13To see LEDs, the card cage side of the system must be exposed; the system top shouldbe on, and the system must be on.CPU LEDsT

2-14 AlphaServer DS20 Service Manual2.8 Compaq AnalyzeCompaq Analyze is the error analysis tool used to analyze errors. An example ofits output i

Troubleshooting 2-15Figure 2-3 shows an example of what you can expect to see on a system’s console,assuming it is a graphics terminal and Compaq

2-16 AlphaServer DS20 Service Manual2.8.2 Description of the ErrorAfter “double clicking” the Problem Found: hot spot on the Compaq Analyzescreen

Troubleshooting 2-17Evidence:Entry Errlog: SMM_1838 SysType_34 OS_Type_1 Entry_Type_682Entry_Type_Ana Mchk_Error_CodEvent_Header_Common_Fields_V2_

2-18 AlphaServer DS20 Service ManualSystype34_Env_Regs_V1Frame_Flags: x00000000Mchk_Error_Code: x00000206Frame_Rev: 1SW_Sum_Flags: x00000000000000

Troubleshooting 2-19Of particular interest in the error report is the Full Description of the error. IfCompaq Analyze is able to determine what f

vii4-19 Removing StorageWorks UltraSCSI Bus Extender...4-40B-1 RCM Connections ...

2-20 AlphaServer DS20 Service Manual2.9 Releasing Secure ModeThe console cannot be secure for most SRM console commands to run. If theconsole is

Error Registers 3-1Chapter 3Error RegistersThis chapter describes the following registers used to hold error information:• Ibox Status Register -

3-2 AlphaServer DS20 Service Manual3.1 Ibox Status Register - I_STATThe Ibox Status Register (I_STAT) is a read/write-1-to-clear register thatcontains

Error Registers 3-33.2 Memory Management Status Register – MM_STATThe Memory Management Status Register (MM_STAT) is a read-only register

3-4 AlphaServer DS20 Service ManualTable 3-2 Memory Management Status RegisterName Bits Type DescriptionReserved <63:11> Reserved for Compaq.D

Error Registers 3-53.3 Dcache Status Register – DC_STATThe Dcache Status Register (DC_STAT) is a read-write register. If a Dcache tagparity erro

3-6 AlphaServer DS20 Service ManualTable 3-3 Dcache Status RegisterName Bits Type DescriptionReserved <63:5> Reserved for Compaq.SEO <4>

Error Registers 3-73.4 Cbox Read Register The Cbox Read Register is read 6 bits at a time. Table 3-4 shows the orderingfrom LSB to MSB. The reg

3-8 AlphaServer DS20 Service ManualTable 3-4 Cbox Read Register (Continued)Name DescriptionIf C_STAT equals xxx_MEM_ERR or xxx_BC_ERR, thenC_STAT co

Error Registers 3-93.5 Miscellaneous Register (MISC)This register is designed so that only writes of 1 affect it. When a 1 is written toany bit

3-10 AlphaServer DS20 Service ManualTable 3-5 Miscellaneous RegisterName Bits TypeInitialState DescriptionRES <63:44> MBZ, RAZ 0 Reserved.DEVS

Error Registers 3-11Table 3-5 Miscellaneous Register (Continued)Name Bits TypeInitialState DescriptionITINTR <7:4> R, W1C 0 Interval time

3-12 AlphaServer DS20 Service Manual3.6 Device Interrupt Request Register (DIRn, n=0,1)These registers indicate which interrupts are pending to the

Error Registers 3-133.7 Pchip Error Register (PERROR)If any bits <11:0> are set, this register is frozen. Only bit <0> can be set af

3-14 AlphaServer DS20 Service ManualTable 3-7 Pchip Error RegisterName Bits TypeInitialState DescriptionSYN <63:56> RO 0 ECC syndrome of error

Error Registers 3-15Table 3-7 Pchip Error Register (Continued)Name Bits TypeInitialState DescriptionRDPE <7> R,W1C 0 PCI read data parity

3-16 AlphaServer DS20 Service Manual3.8 Failure RegisterThis register, on the I2C bus, is locked when there is a power supply or fanfailure. Togethe

Error Registers 3-17Table 3-8 Failure RegisterName Bits TypeInitialState DescriptionPS0_PRESENT_L <7> RO X If the bit is clear, power sup

3-18 AlphaServer DS20 Service Manual3.9 Function RegisterThe Function Register generates an interrupt on the I2C bus if one of the criticalfunctions m

Error Registers 3-19Table 3-9 Function RegisterName Bits TypeInitialState DescriptionReserved <7> RO 0 ReservedPS1_OK_L <6> RO X Wh

ixPrefaceIntended AudienceThis manual is written for the customer service engineer.Document StructureThis manual uses a structured documentation

Removal and Replacement 4-1Chapter 4Removal and ReplacementThis chapter describes removal and replacement procedures for field-replaceable units(FRU

4-2 AlphaServer DS20 Service Manual4.2 FRU ListFigure 4-1 shows of the FRU locations and Table 4-1 lists the part numbers of thefield-replaceable un

Removal and Replacement 4-3Table 4-1 Field-Replaceable Unit Part NumbersCPU Modules54-24758-01 C01 500 MHz CPU, 4 Mbyte cacheMemory Modules54-2506

4-4 AlphaServer DS20 Service ManualTable 4-1 Field-Replaceable Unit Part Numbers (Continued)Power CordsBN26J-1K North America, Japan 12V, 75-inche

Removal and Replacement 4-5Table 4-1 Field-Replaceable Unit Part Numbers (Continued)System Cables andJumpers From To70-31348-01 Interlock switchan

4-6 AlphaServer DS20 Service Manual4.3 System AccessThree sheet metal covers, one on top and one on each side, when removed provideaccess to the sys

Removal and Replacement 4-7Exposing the SystemCAUTION: Be sure the system On/Off button is in the “off” position before removingsystem covers.1. Sh

4-8 AlphaServer DS20 Service Manual4.4 CPU Removal and ReplacementCAUTION: Make sure all CPU modules are the same variant.Figure 4-3 Removing CPU

Removal and Replacement 4-9Removal1. Shut down the operating system and turn the system off.2. Expose the card cage side of the system (see Section